Boiler Blog | Nationwide Boiler Inc.

We proudly promote the Nationwide Boiler CataStak™ Selective Catalytic Reduction (SCR) System for single-digit NOx emissions on package boilers and other fired equipment. Have you ever wondered exactly what NOx is, and, why reducing NOx emissions and your carbon footprint is important?  

NOx refers to nitrogen oxides. It is a generic term for a group of highly reactive gases containing oxygen and nitrogen in varying amounts. NOx forms when fuel is burned at high temperatures, like in a burner combustion process. Package boilers, fired heaters, gas turbines, heat recovery steam generators, and other fired equipment will produce varying levels of NOx, depending on the type of fuel, the burner construction and arrangement, and if any SCR technology is being used.

In short, reducing NOx emissions into the atmosphere will reduce a number of health and environmental hazards linked to the harmful pollutant. NOx has been linked to ground-level ozone, acid rain, water quality deterioration, global warming, and a number of significant respiratory issues.

The EPA and state air boards have been instrumental in the reduction of stack emissions since the 70’s, and Nationwide Boiler has been using and selling CataStak™ SCR systems to continue the trend. Check out this informative article for more detailed information on the harmful effects of NOx and how the EPA is working to control it.

Did you know that Nationwide Boiler's CataStak SCR system can reduce NOx emissions by as much as 99%? Recent source test results from a rental customer in the Central Valley of California prove just that!

Nationwide Boiler is currently renting a 70,000 lb/hr trailer-mounted package watertube boiler and CataStak SCR system to a tomato processing facility with strict emission limits of 5 ppm NOx. The source test was performed under normal season loads, in several 30 minute runs, and tested for NOx, CO and ammonia slip. Results show that the system emitted only 0.7 ppm NOx with 0.39 ppm ammonia slip! In addition to the superior NOx control that our system provides, low ammonia slip illustrates the effectiveness of our design related to the mixing of ammonia and NOx prior to the catalyst.

We are proud that our system can produce such extraordinary results and reduce our customer's emissions to meet the stringent and ever-changing air requirements. For more information, read our latest press release!

Nationwide Boiler's newest innovative product - the DataStak Emissions and Efficiency Monitoring System - was highlighted in the latest issue of Today's Boiler Magazine. See the article here: goo.gl/3n2W4v

The DataStak provides boiler operators with information related to the emissions output and efficiency of their boiler systems. In today's marketplace, this data is not just something that most energy and facility engineers want to know, but many need to know this information for reporting purposes.

We designed the DataStak system to provide real-time, unified data at your fingertips, from one convenient, on-site source. It is more than just a combustion or NOx analyzer. The DataStak is a cost effective, packaged emissions and efficiency monitoring system with O2, NOx, CO, and CO2 measurements, in addition to real time boiler efficiency, fuel usage and carbon footprint calculations.

Representatives from Natiownide Boiler are in Las Vegas, NV this week for Power-Gen, the largest power generation event of the year. Experience the power of the DataStak, live and in-person at the show! Visit us at booth #6019 to learn how the DataStak can help you stay informed on how your boiler is performing.

Have you ever wondered what ppmvd (ref. 3% O2) means? This term is often seen in air permits and is referenced as the emission unit for pollutants such as NOx from boilers.

PPMVD stands for “parts per million by volume, dry”.  For example, “9 ppmvd” refers to (9 / 1,000,000) x 100 = 0.0009% of the volume of flue gas. The reason they stipulate “dry” is because when the emission is measured, the instrument typically removes all moisture (water) from the sample. The “ref. 3% O2” is required as a benchmark for the oxygen content in the flue gas. This is because the boiler will operate at various O2 levels, and the air district needs to normalize the measurements.

Sometimes, emission limits are referenced with different O2 levels for equipment in the same plant.  For example, on a boiler application, NOx may be listed as 9 ppmvd (ref. 3% O2) whereas for a gas turbine it might be 9 ppmvd (ref. 15% O2).  What does it mean when the O2 levels are different?

The difference in the example above is that O2 is referenced at 3% and 15%. Looking at actual numbers will help explain the difference. Let's say a boiler or gas turbine is firing natural gas and the heat input is 100 million Btu/hr. The fuel flow is the same for each case, about 4500 lb/hr. The air flow, however, will be different. 

For boilers, the burner typically runs at about 15% excess air (this is 15% extra air flow above the stoichiometric requirement). In other words, 15% of the air flow passes through the system without being oxidized. This is why the stack O2 (O2 is the extra oxygen in the boiler flue gas flow) is about 3% on a dry basis. This also explains why the 3% O2 benchmark is typically used.Based on the 100 million Btu/hr input and 15% excess air, the boiler air flow is about 81,000 lb/hr. 

On the other hand, gas turbines typically run at higher excess air levels as compared to boilers. To get 15% O2, dry in the stack, the excess air works out to about 230%. The air flow would be about 233,000 lb/hr with the gas turbine application. Stack flow, or the sum of fuel and air, differs in boilers vs. gas turbines:

Boiler stack flow:                            4500 + 81,000 = 85,500 lb/hr
Turbine stack flow:                         4500 + 240,000 = 244,500 lb/hr

You can see that for the same heat input of 100 million Btu/hr, the stack flow will be quite different for these two applications. This also explains why the O2 benchmark is different for these two cases. When comparing the NOx values in lb/mmbtu, we have:

9 ppmvd (ref. 3% O2) NOx firing natural gas is equivalent to 0.011 lb/mmbtu
9 ppmvd (ref. 15% O2) NOx firing natural gas is equivalent to 0.032 lb/mmbtu

This means that even though both 9 ppmvd volumetric numbers are the same, the numbers are actually different on a weight basis (i.e. lb/mmbtu).

Nationwide Boiler provides temporary and permanent solutions with our CataStak SCR System for boilers, gas turbines, and other demanding applications, to meet the most stringent emissions requirements. Contact us today for more infromation. 1-800-227-1966